undici is an HTTP/1.1 client, written from scratch for Node.js.`undici` is vulnerable to SSRF (Server-side Request Forgery) when an application takes in **user input** into the `path/pathname` option of `undici.request`. If a user specifies a URL such as `http://127.0.0.1` or `//127.0.0.1` ```js const undici = require("undici") undici.request({origin: "http://example.com", pathname: "//127.0.0.1"}) ``` Instead of processing the request as `http://example.org//127.0.0.1` (or `http://example.org/http://127.0.0.1` when `http://127.0.0.1 is used`), it actually processes the request as `http://127.0.0.1/` and sends it to `http://127.0.0.1`. If a developer passes in user input into `path` parameter of `undici.request`, it can result in an _SSRF_ as they will assume that the hostname cannot change, when in actual fact it can change because the specified path parameter is combined with the base URL. This issue was fixed in `undici@5.8.1`. The best workaround is to validate user input before p…

Authorization headers are cleared on cross-origin redirect. However, cookie headers which are sensitive headers and are official headers found in the spec, remain uncleared. There are active users using cookie headers in undici. This may lead to accidental leakage of cookie to a 3rd-party site or a malicious attacker who can control the redirection target (ie. an open redirector) to leak the cookie to the 3rd party site. This was patched in v5.7.1. By default, this vulnerability is not exploitable. Do not enable redirections, i.e. `maxRedirections: 0` (the default).

undici is an HTTP/1.1 client, written from scratch for Node.js. It is possible to inject CRLF sequences into request headers in undici in versions less than 5.7.1. A fix was released in version 5.8.0. Sanitizing all HTTP headers from untrusted sources to eliminate `\r\n` is a workaround for this issue.

`Undici.ProxyAgent` never verifies the remote server's certificate, and always exposes all request & response data to the proxy. This unexpectedly means that proxies can MitM all HTTPS traffic, and if the proxy's URL is HTTP then it also means that nominally HTTPS requests are actually sent via plain-text HTTP between Undici and the proxy server.